JP2001304266A - Super thin wall type rolling bearing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve an acoustic characteristic by lowering a noise level of a super thin wall type rolling bearing. SOLUTION: The rolling bearing is furnished with an outer member 1 having a raceway surface 1a on an inner periphery, an inner member 2 having a raceway surface 2a on an outer periphery, a plural number of rolling elements 3 interposed between the raceway surfaces of the outer member 1 and the inner member 2 and a holder 4 to equally arrange each of the rolling elements in the circumferential direction. On this bearing, a ratio of a diameter DB of the rolling element 3 and a pitch circle diameter PCD of the bearing is made to be less than 0.03. Additionally, by specifying thickness in the radial direction of the holder 4 as L and a difference of a radius of an inner peripheral surface 1b of the outer member 1 and a radius of an outer peripheral surface 2b of the inner member 2 as M, their ratio L/M is made more than 0.8 and less than 0.95.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to an industrial robot,
The present invention relates to an ultra-thin type rolling bearing used for a machine tool, a medical device, and the like.

[0002]

2. Description of the Related Art FIG. 5 shows an example of a CT scanner as a kind of medical equipment. As shown in the figure, the CT scanner irradiates an X-ray generated by an X-ray tube device 20 to a subject 23 through a wedge filter 21 for equalizing the intensity distribution and a slit 22 for limiting the intensity distribution.
X-rays that have passed through the subject 23 are received by the detector 24, converted into electric signals, and sent to a computer (not shown). Each component such as the X-ray tube device 20, wedge filter 21, slit 22, and detector 24 is mounted on a substantially cylindrical rotating base 27 rotatably supported on a fixed base 26 via a bearing 25. The rotation of the gantry 27 rotates around the subject 23. In the CT scanner device, the X-ray tube device 20 and the detector 24
The projection data covering all angles at all points in the examination section of the subject 23 is obtained by the rotational movement around the subject 23, and a tomographic image is obtained from these data by a pre-programmed reconstruction program.

In this CT scanner, the inner peripheral surface of the fixed gantry 26 is formed to have a large diameter (about 1 m in diameter) enough to accommodate the subject 23, so that a bearing 25 between the fixed gantry 26 and the rotary gantry 27 is provided. For this, a so-called ultra-thin rolling bearing whose cross section is significantly smaller than its diameter is used. As shown in FIG. 6, the ultra-thin rolling bearing 25 has an outer member 1 'having a raceway surface 1b' on the inner periphery and a raceway surface 2 on the outer periphery.
A plurality of rolling elements 3 'interposed between the raceway surfaces 2b' and 1b 'of the inner member 2' having the b 'and the inner and outer members 2' and 1 '.
(A ball in the illustrated example), and a retainer 4 'for equally arranging the rolling elements 3' in the circumferential direction.

[0004] Of the ultra-thin type rolling bearings, PCD is 50
The retainer 4 'of a large diameter bearing reaching 0 mm or more is manufactured in an annular shape by joining, for example, brass-based metal plates (segments) formed in an arc-shaped cross section by welding or the like. Each segment is formed with a pocket for accommodating the rolling element 3 ', and the rolling element 3' is accommodated in this pocket, whereby each rolling element 3 'is held at equal intervals in the circumferential direction. There is a pocket gap between the pocket of the retainer 4 'and the surface of the rolling element 3', so that the mutual movement has a degree of freedom.

[0005]

In a small bearing, neither the inner peripheral surface nor the outer peripheral surface of the cage is in contact with the inner member or the outer member. You will be guided for rotation. On the other hand, in the large diameter ultra-thin type rolling bearing as described above, the inner peripheral surface of the retainer 4 ′ is brought into contact with the outer peripheral surface of the inner member 2 ′, or the outer peripheral surface of the retainer 4 ′ is The rotation of the retainer 4 'is guided by contacting the inner peripheral surface of the member 1'. In this case, since the misalignment between the rotation center of the bearing and the rotation center of the cage increases, the whirling amount of the cage increases, which may cause noise.

There is also a concern that the noise level may increase depending on the contact state between the inner member or the outer member and the retainer.

SUMMARY OF THE INVENTION An object of the present invention is to reduce the noise level of an ultra-thin type rolling bearing and improve the acoustic characteristics.

[0008]

In order to achieve the above object,
In the present invention, the outer member having a raceway surface on the inner periphery, the inner member having a raceway surface on the outer periphery, a plurality of rolling elements interposed between the outer member and the raceway surface of the inner member, In an ultra-thin type rolling bearing comprising a cage in which rolling elements are equally arranged in a circumferential direction, a ratio of a diameter of the rolling element to a pitch circle diameter of the bearing is 0.03 or less, and a radius of the cage is Assuming that the thickness in the direction is L and the difference between the radius of the inner peripheral surface of the outer member and the radius of the outer peripheral surface of the inner member is M, the ratio L / M is 0.8 or more and 0.95 or more.
I did it below.

The range of the L / M value is larger than that of the conventional product. Therefore, the width of movement of the cage 4 in the radial direction is more restricted than that of the conventional product, whereby the center of rotation of the cage approaches the center of rotation of the bearing, and the amount of whirling of the cage 4 in the radial direction is reduced. It is possible to suppress the generation of noise due to the whirling of the container.

[0010] radial thickness L and the rolling element diameter D _B of the cage
The ratio L / D _B of A, 0.4 or more, may be set to 0.5 or less.

By forming a lubricant reservoir on one or both of the inner peripheral surface and the outer peripheral surface of the retainer, the lubricant accumulated in the reservoir portion allows the retainer to communicate with the inner member and the outer member. Abundant oil is supplied to the contact portion with the member.
Therefore, generation of noise due to friction between the retainer and a member that comes into contact with the retainer can be suppressed.

By making the cage made of resin, the weight of the cage is reduced as compared with the case made of metal, so that the noise level can be further reduced.

One of the outer member and the inner member can be fixed to a rotating frame of a CT scanner that rotates around a subject, and the other can be fixed to a fixed frame of the CT scanner. Thereby, the rotating gantry of the CT scanner device is rotatably supported with respect to the fixed gantry.

[0014]

BRIEF DESCRIPTION OF THE DRAWINGS FIG.
A description will be given based on FIG.

FIG. 1 is a sectional view of a bearing 25 used in the CT scanner shown in FIG. 5, which is an example of an ultra-thin rolling bearing. The bearing 25 has a ring-shaped outer member 1 having a single row of raceway surfaces 1a on the inner periphery, and a ring-shaped outer member having a single row of raceway surfaces 2a arranged concentrically on the inner circumference side of the outer member 1. A plurality of rolling elements 3 interposed in a single row between the raceway surfaces 1a and 2a of the outer member 1 and the inner member 2;
A cage 4 for holding the rolling elements 3 at equal intervals in the circumferential direction;
A sealing device 5a for sealing the openings at both ends of the bearing in a non-contact manner;
5b is a main component. In the drawings, a ball is exemplified as the rolling element 3, but a roller may be used.

The bearing 25 has a diameter (diameter) D of the ball 3.
The ratio φ between _B and the pitch circle diameter (diameter) PCD is 0.03 or less (φ
= D _B /PCD≦0.03). For example, the ball diameter is 1/2 inch (12.7 m).
m), PCD is 1041.4 mm, ratio φ of both is 0.01
Set to 2. The present invention mainly has a PCD of 500 mm
It is applied to a large diameter bearing of about 1500 mm.

A mounting hole 8 is formed in one end side (right side in the drawing) of the outer member 1. The outer member 1 is screwed into the mounting hole 8 by a fastening means such as a bolt (not shown), so that the outer member 1 is moved to the position shown in FIG. Is fixed to the rotating frame 27 of the CT scanner device shown in FIG. A mounting hole 9 is similarly formed on the other end surface of the inner member 2, and the inner member 2 is fixed to the fixed base 26 by screwing a fastening means such as a bolt (not shown) into the mounting hole 9. You. From the above, the outer member 1 becomes a rotating member that rotates together with the rotary gantry 27, and the inner member 2
Is a non-rotating fixing member. Depending on the structure of the CT scanner device, the outer member 1 may be on the fixed side, and the inner member 2 may be on the rotating side that rotates together with the rotating gantry 27, contrary to the above.

The cage 4 is different from the conventional metal material,
It is formed of a resin material. As shown in FIG. 2, the resin cage 4 includes a plurality of resin segments 40 each having an arc-shaped cross section.
Are connected in the circumferential direction to form a ring-shaped divided type.
As shown in FIG. 3, the concave or convex fitting portions 44a and 44b formed at both ends of each segment 40 are combined with the convex or concave fitting portions 44b of the segment ends to be joined.
Each of the segments 40 is connected by being fitted into the groove 44a and engaging with each other in the circumferential direction, so that the annular retainer 4 is formed. The segment 40 in the illustrated example is provided between a base 41 having an arc shape obtained by dividing an annular body at a plurality of positions in a circumferential direction, a column 42 extending in the axial direction from the base 41, and an adjacent column 42. Pockets 43a, 43
b.

The illustrated pockets 43a and 43b have two types of shapes, one of which is a first pocket 43a having a function of holding the ball 3 (including an equal distribution function).
The other is the second pocket 43b having only the equal distribution function of the ball 3. The cage 4 of the present embodiment is provided with the two types of pockets 43a and 43b alternately at equal intervals in the circumferential direction.

As shown in an enlarged manner in FIG. 4 (FIG. A is a front view as viewed from the direction A in FIG. B, and FIG. B is a plan view), the first pocket 43a is separated, for example, between opposing surfaces. A pair of tapered portions a1 whose distance gradually increases toward the opening side, a pair of straight portions a2 along the axial direction, and a concave spherical portion a3 having a curvature slightly larger than the curvature of the ball 3 are formed from the opening side. It is configured by being arranged sequentially. The tapered portion a1 and the straight portion a2 are flat surfaces extending in the radial direction. The distance between the straight portions a2 is slightly smaller than the diameter of the ball 3, so that the straight portion a2 restricts the ball 3 from jumping toward the pocket opening side, and holds the ball 3 in the pocket 43a ( Ball holding function).

On the other hand, the second pocket 43b has, for example, a concave spherical portion b1 having a curvature slightly larger than the curvature of the ball 3, and a pair of cylindrical portions b2 extending axially and tangentially from the spherical portion b1. It is composed of The ball 3 accommodated in the second pocket 43b is movable in the axial direction.
It does not have the function of holding the ball 3 as shown in FIG.

The ball 3 is accommodated in the pockets 43a and 43b by pushing the ball 3 from the openings of the pockets 43a and 43b toward the back of the pocket. At this time, in the first pocket 43a, it is necessary to push in the ball 3 while pushing and expanding the tapered portion a1, but in the second pocket 43b, such a trouble is not required. Can be simplified.

The shapes and structures of the pockets 43a and 43b described above are merely examples, and pockets having various shapes and structures may be employed in accordance with the conditions of use of the bearing, such as a single pocket. Can be.

The first pocket 43a and the second pocket 4
In any of 3b, there is a pocket gap between the ball 3 surface and the pocket inner surface. During the rotation of the bearing, the cage 4 moves relative to the ball 3 in the radial direction due to the pocket gap. With this relative movement, the retainer 4 comes into contact with one of the outer peripheral surface 2b of the inner member 2 and the inner peripheral surface 1b of the outer member 1, and the rotation of the retainer 4 is guided. In the present embodiment, the case where the outer peripheral surface 45 of the retainer 4 comes into contact with the inner peripheral surface 1b of the outer member 1 is illustrated. In this case, the retainer 4 is moved outward by contact with the outer member 1. It rotates by receiving a driving force from the member 1.

In the present invention, the radial thickness L of the cage 4 is
And the ratio L / M of the space dimension M expressed by the difference between the radius of the inner peripheral surface 1b of the outer member 1 and the radius of the outer peripheral surface 2b of the inner member 2 is 0.8 or more and 0.95 or less. (0.8 ≦ L / M ≦ 0.95). In conventional products, this L /
Although M is set to about 0.5 to 0.7, in the present invention, the L / M value is set to be larger than that of the conventional product, and
Was limited in the radial movement width. As a result, the rotation center of the cage 4 approaches the rotation center of the bearing, so that the amount of whirling of the cage 4 in the radial direction is reduced, and the generation of noise due to the whirling of the cage 4 is suppressed, and the acoustic characteristics are reduced. Can be improved. When the retainer 4 is made of resin as described above, the weight of the retainer 4 itself can be reduced, which is more effective because the noise level is reduced.

The reason why L / M is set within the above range is that if L / M is smaller than 0.8, the effect of suppressing the whirling of the retainer 4 cannot be sufficiently obtained, so that the acoustic characteristics are improved. When the effect is not obtained and L / M is larger than 0.95, the retainer 4 frequently comes into contact with the outer member 1, and there is a possibility that the lubricating property of the contact portion may be impaired. Because.

[0027] Here, the radial thickness L of the cage 4, the ratio of 0.4 to 0.5 relative to the diameter D _B of the ball 3 (0.4
≤ L / D _B ≤ 0.5 (L / D _B is smaller than 0.4 in the conventional product).

As a part of the above acoustic measures, the present invention provides:
Around the pockets 43a and 43b of the retainer outer peripheral surface 45,
A pool 47 for storing a lubricant such as grease is formed. The pool portion 47 is formed by partially recessing the cage outer peripheral surface 45 around the pockets 43a, 43b. In FIG. 4, the entire length of the cage 4 in the axial direction is formed so as to include the entire region of the pockets 43a, 43b. The illustrated example is a pool portion 47 formed over the same. The pool portion 47 is formed between at least the inner member 2 and the inner and outer peripheral surfaces 46 and 45 of the cage 4.
And on the peripheral surface on the side in contact with the outer member 1. Therefore, when the retainer 4 is brought into contact with the outer member 1 to rotate the retainer 4 as in the present embodiment, the pool portion 47 is formed at least on the outer peripheral surface 45 of the retainer 4 as described above. When the cage 4 is brought into contact with the inner member 2, a pool portion 47 is formed at least on the inner peripheral surface 46 of the cage 4.
In any case, the inner and outer peripheral surfaces 4 of the cage 4
Reservoir 47 may be formed on both 6 and 45.

Since grease as a lubricant accumulates in the pool portion 47 during rotation of the bearing, the outer circumferential surface 4
At the time of contact between the inner member 5 and the inner peripheral surface 1b of the outer member 1, an abundant amount of oil is supplied to the contact portions of the outer member 1 and the track surfaces 1a, 2a. Therefore, the contact between the retainer 4 and a member (the outer member 1 in the present embodiment) that comes into contact with the retainer 4 or the ball 3
Generation of noise due to contact between the motor and the raceway surfaces 1a, 2a can be suppressed, and the acoustic characteristics are improved.

In the above description, the rotation of the retainer 4 is guided by bringing the outer peripheral surface 45 of the retainer 4 into contact with the inner peripheral surface 1b of the outer member 1. The peripheral surface 46 is brought into contact with the outer peripheral surface 2 b of the inner
The same can be applied to the case of guiding the rotation of. In this case, as described above, the pool portion 47 is formed at least on the inner peripheral surface 46 of the retainer 4 (and may be formed on the outer peripheral surface 45).

[0031]

According to the present invention, since the L / M value is set to be larger than that of the conventional product to limit the amount of movement of the cage in the radial direction, the rotation center of the cage becomes the rotation center of the bearing. When approaching, the generation of noise due to the whirling of the cage can be suppressed, and the acoustic characteristics can be improved.

By forming a lubricant reservoir on one or both of the inner peripheral surface and the outer peripheral surface of the retainer, the lubricant accumulated in the reservoir portion allows the retainer to communicate with the inner member and the outer member. Sufficient oil is supplied to the contact portion with the member.
Therefore, generation of noise due to friction between the two is suppressed.

By using an ultra-thin type rolling bearing having improved acoustic characteristics as described above in a CT scanner,
Stress applied to the subject (patient) due to noise at the time of measurement can be reduced.

[Brief description of the drawings]

FIG. 1 is a sectional view of an ultra-thin type rolling bearing according to the present invention.

FIG. 2 is a front view of the retainer.

FIG. 3 is a developed plan view of a segment constituting the cage.

FIG. 4 is an enlarged view of the retainer pocket, (A)
The figure is a view on arrow A in the figure (B), and the figure (B) is a developed plan view.

FIG. 5 is a sectional view of a CT scanner device.

FIG. 6 is a cross-sectional view of a rolling bearing (ball bearing).

[Explanation of symbols]

 Reference Signs List 1 outer member 1a raceway surface 1b inner peripheral surface 2 inner member 2a raceway surface 2b outer peripheral surface 3 rolling element (ball) 4 retainer 43a first pocket 43b second pocket 45 outer peripheral surface 46 inner peripheral surface 47 reservoir

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI theme coat ゛ (Reference) F16C 33/56 F16C 33/56 33/58 33/58 33/66 33/66 Z

Claims (5)

[Claims] An outer member having a raceway surface on an inner periphery, an inner member having a raceway surface on an outer periphery, a plurality of rolling elements interposed between the raceways of the outer member and the inner member; An ultra-thin type rolling bearing comprising a cage for equally arranging each rolling element in a circumferential direction, wherein a ratio of a diameter of the rolling element to a pitch circle diameter of the bearing is 0.0.
3, and the ratio L / M is 0.8 or more, where L is the radial thickness of the cage, and M is the difference between the inner peripheral surface radius of the outer member and the outer peripheral surface radius of the inner member. , 0.95 or less. 2. The radial thickness L of the cage and the rolling element diameter D
_2. The ultra-thin type rolling bearing according to claim 1, wherein a ratio L / DB to _{B is set} to 0.4 or more and 0.5 or less. 3. The ultra-thin rolling bearing according to claim 1, wherein a lubricant reservoir is formed on one or both of an inner peripheral surface and an outer peripheral surface of the cage. 4. The ultra-thin rolling bearing according to claim 1, wherein the cage is made of resin. 5. The apparatus according to claim 1, wherein one of the outer member and the inner member is fixed to a rotating frame of the CT scanner device that rotates around the subject, and the other is fixed to a fixed frame of the CT scanner device. The ultra-thin rolling bearing according to any one of claims 1 to 4.